- 4 eggs
- 1 tablespoon whole milk
- 4 pinches ground black pepper
- 2 pinches garlic salt, or to taste
- 2 teaspoons olive oil
- 4 cremini mushrooms, sliced
- 2 tablespoons chopped red onion
- 1 cup baby spinach, coarsely chopped
- 1/2 ounce crumbled Stilton cheese
- 1/2 cup shredded part-skim mozzarella cheese
- Lightly whisk the eggs with the milk in a bowl to break the yolks and integrate the milk; season with 4 pinches black pepper and 2 pinches garlic salt.
- Heat olive oil in a non-stick skillet over medium heat; cook and stir mushrooms and onion in hot oil until the onion softens, about 5 minutes.
- Spread the mushrooms and onion into the bottom of the skillet so it forms an even layer.
- Sprinkle spinach evenly across the top of the mushroom and onion layer.
- Pour egg mixture over the vegetables.
- Cook until the top of the egg is set, 3 to 5 minutes.
- Sprinkle Stilton cheese and mozzarella cheese over the cooked egg; cook until the mozzarella begins to melt, fold the omelet in half around the filling to make a half-moon.